The recent development of techniques to perform high resolution nuclear magnetic resonance (NMR) experiments in solids has opened the way for NMR studies of biological membranes and unsonicated phospholipid bilayer model systems. Preliminary 31P NMR experiments has shown interesting effects when Ca2 ion is added to bilayer dispersions of phosphatidylserine. The question of phospholipid-cation interactions is one of considerable biological significance, and the 31P and 2H NMR experiments described in this proposal explore the nature of the phosphatidylserine/Ca2 ion interaction. The 31P and 2H NMR experiments will be performed on a high power multi-nuclear NMR spectrometer under construction in our laboratory and described in this proposal.